I think it really started as a discussion as to whether it could be described as a "72A ring" - and, as I said, it's really a question of what you mean by that. Yes, as I've just written to stillp, it would be possible to arrange a 72A load such that the current through neither MCB exceeded its In, but (with other arrangements of the load) it would also be possible for a current under 40A to put more than 32A through the 32A MCB, or for a current not much more than 40A to result in more than 40A flowing through the 40A MCB.Yes, but the discussion is: would the circuit load be limited to 32A or could it rise to 72A?
It therefore comes down to what you want to mean by an "X amp ring circuit".
Kind Regards, John